In an alternating current electric power system, synchronization is the process of matching the frequency and speed of a generator to a power grid. An AC generator cannot deliver power to the power grid unless it is running at the same frequency as the grid.
When the power grid has two or more generators connected thereto, or two generators are provided on separate power grids but there may be a transfer of power between the two generators, the generators also need to be synchronized together in frequency and phase. Poor phase matching can lead to high transient torque with high currents, which can damage the windings of the generator, and high instant voltages, which can damage the insulation of the equipment.
The typical power plant arrangement of an aircraft is one generator per driving unit, whether for a diesel engine, a gas turbine engine or a steam turbine. Driving two generators through the same gear box, thus mechanically interconnected, requires mechanical phase matching between the twin generators. There is a need to improve on the existing methods for synchronizing generators together.